Due to the size and complexity of structural components such as aircraft wings, sections of aircraft fuselage, etc., the formation of such structures using composite materials in a single step molding procedure has historically not been possible. Until recently, a process capable of holding critical dimensional features within narrow tolerance ranges for large complex composite structures did not exist.
In previous manufacturing operations, typically the complex part is broken down into multiple pieces of simple design that are subsequently assembled into a single large complex structure. The cost to manufacture the structure thus increases significantly through the additional manufacturing steps needed to fabricate separately and then assemble (i.e., often bond adhesively or mechanically attach) two or more independent component parts to form a single overall structure.
Accordingly, it would be highly desirable to provide a molding process in which separate structural elements (i.e., such as skins and stiffening elements) could be secured to one another in a continuous fashion in a preliminary manufacturing step and then subsequently molded in a single molding step to form a unified structure. Such a process would significantly reduce the cost and time associated with producing complex built-up structural components of military and commercial aircraft such as wing boxes and other internally-stiffened structural components which heretofore have been manufactured through a plurality of separate molding processes to produce independent parts, which are then subsequently secured together by bonding, riveting or other mechanical means. Such a single step molding process to produce unified composite assembly structure also offers the potential to increase damage tolerance for the structure in view of the additional strength that would be expected from molding several independent component parts together in a single molding step to produce joints having more uniform load paths that are absent of stress concentrations over what would be possible with subsequently bonded or mechanically-attached part interfaces.